Mobile apparatus such as cellphones and notebook personal computers have a wireless communication function for performing a data communication with an external apparatus.
FIG. 6 shows the configuration of a wireless LAN device disclosed in Patent document 1. The wireless LAN device shown in FIG. 6 is composed of an IC chip 4 which performs radio-frequency signal processing, an IC chip 2 which performs baseband signal processing, an oscillator 3 which supplies a clock signal to the IC chip 2, an oscillator 5 which supplies a clock signal to the IC chip 4, and an antenna 6. The wireless LAN device receives, from a host CPU 1, information to be sent to another terminal, modulates it, and sends out a resulting signal from the antenna 6. Furthermore, the wireless LAN device receives a signal transmitted from another terminal by the antenna 6, demodulates it, and transfers a resulting signal to the host CPU 1.
The IC chip 2 is supplied with a clock signal from the oscillator 3. This clock signal is used for allowing an intra-chip CPU 22 to operate. The IC chip 4 is supplied with a clock signal from the oscillator 5. This clock signal is also supplied to the IC chip 2 via the IC chip 4. A BB processing unit 24 and a MAC processing unit 23 which are provided in the IC chip 2 operate on the clock signal that is supplied via the IC chip 4.